Ships Reserve tank sizes for all ships

[size=+2]Fuel tanks[/size]
[size=+1]The main tank[/size]
We all know that our ships have one or more fuel tanks from which the frame shift drive draws fuel when jumping between systems. The amount of fuel available in these tanks is shown in a thick bar on the right of the HUD. When we plot a jump, a portion of that bar turns blue to show how much fuel will be expended by the jump, and after the jump the bar shrinks accordingly.

This bar represents the amount of fuel in the main tank. If you've ever allowed it to run out you will have seen and heard the message "main fuel tank drained" warning you of that fact.

[size=+1]The reserve tank[/size]
There is another, thinner bar, shown above the main tank bar. This bar represents the reserve tank. The reserve tank is steadily drained by active modules on your ship. The rate of drain is shown above the bar. When the reserve tank is empty, fuel is automatically taken from the main tank to top it back up. Unless the main tank is empty, in which case you need to call the Fuel Rats because your ship is about to explode.

Fuel in the reserve tank cannot be consumed by the frame shift drive, although its mass does contribute to jump cost calculations. Furthermore, the reserve tank cannot be replenished by fuel scooping. If you are within the scooping zone of a star you can observe that the fuel scoop will deactivate when the main tank is filled. If the reserve tank runs empty while you are still in the zone, it will be topped up from the main tank and fuel scooping will briefly resume to replace the fuel which was moved to the reserve.

[size=+1]Why is the reserve tank important?[/size]
Needless to say, the fact that your ship cannot operate without fuel in the reserve tank is worthy of note, at least in an abstract sense. The automatic topup mechanism from the main tank makes the threat of ship destruction less ominous in most circumstances.

Apart from that, the mass of the fuel in the reserve tank does contribute to the fully laden mass of the ship and must be taken into account when calculating jump range and fuel cost.

Reducing the number of (time-consuming) hyperspace jumps is a common tactic in Buckyball races. When CMDR Alot travelled from Sol to Sagittarius A* in under two hours he optimised his route down to the level of plotting jumps that would only be possible with a particular amount of fuel in his reserve tank. I myself have won races by planning routes that required specific numbers of 10% refuels at stations.

As we shall see, the Refuel 10% action at stations does not simply refill 10% of the main tank size. It also refills 10% of the reserve tank. That extra fuel can be the difference between making a long jump or not being able to.

[size=+1]Determining the size of the reserve tank[/size]
When docked at a station which offers refueling facilities, we can choose to Refuel All or Refuel 10%. The amount of fuel actually purchased for a 10% refuel shows up in the journal file as a property of the RefuelPartial event.
Code:
{ "timestamp":"2017-09-10T21:24:30Z", "event":"RefuelPartial", "Cost":42, "Amount":0.836000 }
When experimenting with 10% refuels and looking at the RefuelPartial events recorded in the journal, I made some observations.

  • When the ship's total fuel level is 90% or more, the Refuel All and Refuel 10% actions have the same cost.
  • When the ship's total fuel level is below 90%, a 10% refuel always costs the same amount of credits and dispenses the same amount of fuel given the same size of main tank.
  • When the ship's total fuel level is below 90%, a 10% refuel always dispenses more than (size of main tank) x 10% fuel.
The extra fuel is 10% of the reserve tank and that means we have a method to calculate the size for each ship.

  • Drain the main tank below 90%, for example by making one or more hyperspace jumps.
  • Purchase a 10% refuel.
  • Consult the journal to see how much fuel we actually purchased.
  • Subtract (size of main tank) x 10% from the amount recorded in the journal.
  • Multiply the remainder by 10.
The result of the above calculation is the ship's reserve tank size.

Note that it is important that the main tank be at less than 90% capacity for this experiment. When the tank is 90% full, the Refuel 10% action will always top it up completely regardless of the actual amount of fuel present. It will therefore not be possible to break down the fuel allocation.

Example:
An Adder with an 8T fuel tank is refuelled by 10%.

The fuel dispensed is 0.836T.

10% of 8T is 0.8T.

Therefore 10% of the Adder's reserve tank size is (0.836 - 0.8) = 0.036T.

We conclude that the Adder has a reserve tank size of (0.036 x 10) = 0.36T.

[size=+1]Reserve tank sizes for every ship[/size]
Please feel free to check and correct. You can imagine how tediously boring this research was, so mistakes are quite possible.
ShipTank
Hauler0.25
Sidewinder0.30
Eagle0.34
Adder0.36
Imperial Eagle0.37
Type 60.39
Keelback0.39
Viper Mk III0.41
Imperial Courier0.41
Viper Mk IV0.46
Asp Scout0.47
Cobra Mk III0.49
Diamondback Scout0.49
Mamba0.50
Dolphin0.50
Cobra Mk IV0.51
Diamondback Explorer0.52
Type 70.52
Vulture0.57
Krait Mk II0.63
Krait Phantom0.63
Asp Explorer0.63
Fer-de-Lance0.67
Federal Assault Ship0.72
Imperial Clipper0.74
Alliance Challenger0.77
Alliance Crusader0.77
Type 100.77
Type 90.77
Alliance Chieftain0.77
Orca0.79
Beluga0.81
Federal Gunship0.82
Federal Dropship0.83
Python0.83
Anaconda1.07
Federal Corvette1.13
Imperial Cutter1.16
 
Last edited:
Great work. I was thinking of adding this information to the ship stats tables in the Wiki, e.g. http://elite-dangerous.wikia.com/wiki/Hauler, but the table is restricted to a template with predefined fields. I've proposed this on the template's talk page, but the post did not show up (not sure if it just needs moderator approval or I did something wrong, I am not so well versed with editing wikis).
 
Are you out by a factor of 10?

The Sidewinder has a 0.3 ton reserve tank from the outfitting screen, and you have 0.03 tons

This is verified by fuel usage when using X.XX tons per hour and the reserve draining is ~1/3 of that time expected if it was one tonne

Your Example:
An Adder with an 8T fuel tank is refuelled by 10%.

The fuel dispensed is 0.836T.

10% of 8T is 0.8T.

Therefore the Adder has a reserve tank size of (0.836 - 0.8) = 0.036T.\

Should be

An Adder with an 8T fuel tank is refuelled by 10%.


The fuel dispensed is 0.836T.


10% of 8T is 0.8T.


Therefore 10% of the Adder's reserve tank size of (0.836 - 0.8) = 0.036T

so the reserve tank is 0.036/0.1 or 0.36 tonnes
 
You are right. I confirmed by running a 2T tank on a Cutter that my initial theory that Refuel 10% includes a full topup of the reserve tank is wrong.

That would probably have been obvious to me if I could actually read the UI in outfitting where the additional fuel is reported.

I'll update the OP.

As for this question,
Is this more or less accurate than just starting with a full reserve tank and timing how long it takes to trigger a reserve top-off?
The journal reports the fuel purchased to several decimal places whereas the UI only uses two. That would affect the results even if you timed it accurately.
 

Robert Maynard

Volunteer Moderator
The total fuel amount is reported in status.json (in Beta) - and, having fully refuelled, the size of each reserve tank can be simply calculated by subtracting the capacity of the ship's main tank(s).
 
Fuel tanks
The main tank
We all know that our ships have one or more fuel tanks from which the frame shift drive draws fuel when jumping between systems. The amount of fuel available in these tanks is shown in a thick bar on the right of the HUD. When we plot a jump, a portion of that bar turns blue to show how much fuel will be expended by the jump, and after the jump the bar shrinks accordingly.

This bar represents the amount of fuel in the main tank. If you've ever allowed it to run out you will have seen and heard the message "main fuel tank drained" warning you of that fact.

The reserve tank
There is another, thinner bar, shown above the main tank bar. This bar represents the reserve tank. The reserve tank is steadily drained by active modules on your ship. The rate of drain is shown above the bar. When the reserve tank is empty, fuel is automatically taken from the main tank to top it back up. Unless the main tank is empty, in which case you need to call the Fuel Rats because your ship is about to explode.
You call it the reserve tank. I call it the day tank as it supplies fuel to run all the utilities. Since it is constantly being drained. I can hardly think of it as a reserve.

Other than that. Good work on the volumes. Now with the fuel consumption we can work out how long the day tank will last before it is refilled from the main tank. There has been times when exploring in Brown Dwarf deserts I would have liked to know when the main tank would have to supply more fuel to it.
 
. Now with the fuel consumption we can work out how long the day tank will last before it is refilled from the main tank. There has been times when exploring in Brown Dwarf deserts I would have liked to know when the main tank would have to supply more fuel to it.
Your ship and SRV displays fuel usage in tonnes per hour so easy once you know your tank size
 

Robert Maynard

Volunteer Moderator
Out of interest, how would you do it?
One way is to use the fuel parameter published in status.json - and calculate the change in it with regard to time between successive publications, firstly having noted the fuel level from the last game start or fuel-scooping event.

Sadly, status.json is only published as required (i.e. when something changes, i.e. flags, fire-group, GUI focus, etc., subject to minimum positional changes required, when the HasLatLong flag is active, to prompt republication). I did not get round to working out whether there is a republication prompt on fuel use.
 
One way is to use the fuel parameter published in status.json - and calculate the change in it with regard to time between successive publications, firstly having noted the fuel level from the last game start or fuel-scooping event.

Sadly, status.json is only published as required (i.e. when something changes, i.e. flags, fire-group, GUI focus, etc., subject to minimum positional changes required, when the HasLatLong flag is active, to prompt republication). I did not get round to working out whether there is a republication prompt on fuel use.
[FONT=&quot]The scenario I was thinking of is where your ship has entered a non scoopable star system and you are super cruising to a distant in-system target. Will there be enough fuel to get there and still have enough to jump out of the system?[/FONT]
It would be a simple thing to trigger republication by changing the fire group or mode etc. (since you say so). I was thinking of a simpler solution as Vasious said it was so easy once you know your tank size.
I think know how I would do it.
 

Robert Maynard

Volunteer Moderator
[FONT="]The scenario I was thinking of is where your ship has entered a non scoopable star system and you are super cruising to a distant in-system target. Will there be enough fuel to get there and still have enough to jump out of the system?[/FONT]
It would be a simple thing to trigger republication by changing the fire group or mode etc. (since you say so). I was thinking of a simpler solution as Vasious said it was so easy once you know your tank size.
I think know how I would do it.
Current main tank level is published on arrival in a system, in the FSDJump event. Taking the total fuel reading from status.json published on arrival (when the FSD Cooldown flag is flipped on) will allow the current reservoir level to be calculated.

As you say, status.json republication can be prompted at will.

I'll watch this topic - it's an interesting problem - not least due to the somewhat unpredictable duration of long range SuperCruise. :)

[edit] Actually, the topic itself has prompted me to add a "time to empty" estimate, based on monitoring total fuel over time, to my StatusDisplay app. [/edit]
 
Last edited:
With out the "Reserve" tank. One wouldn't have enough fuel to maintain life supporting mods or others while waiting for a Fuel Rat to assit them.

Motorcycles have a selector that they can if and when they run out of fuel, switch and make it to a fuel stop. However, if they don't switch it back to normal after they've filled up and they run out again, they are screwed. I use to assist them every once in a while, but lately it seems to be happening much to much thus I've stopped doing it entirely.
 
The scenario I was thinking of is where your ship has entered a non scoopable star system and you are super cruising to a distant in-system target. Will there be enough fuel to get there and still have enough to jump out of the system?
It would be a simple thing to trigger republication by changing the fire group or mode etc. (since you say so). I was thinking of a simpler solution as Vasious said it was so easy once you know your tank size.
I think know how I would do it.
Oh I was just meaning

Lets take my Sidewinder

It has 0.3 tonne reserve tank and a 2 tonne main take

Lets say I was cruising over a planet in normal space looking for Fumeroles.

With everything turned off it has a fuel usage of 0.36 tonnes an hour, based on the figure above the signature line on the HUD

So we plot a route to the nearest scoopable star and eyeball the fuel needed, and we find it is 0.1 tonnes of fuel as it is not far

(fuel usage for jump can be found here and not hard to make a google sheets calculator set up for your current ship)


So we have the reserve tank of 0.3 to use before it refills from the main tank.
But we cannot assume we have 1.9 tonnes in the main tank, as it refuels a full reserve tank at a time

So we need to keep 0.2 in the main tank

So that gives us 1.8+0.3 or 2.1 tonnes or 2100 liters of hydrogen
2100/360 per hour is 5 hours 50 minutes before it is time to jump


Of-course Super cruise uses more power and thus fuel so travel to the planet needs to be factored in
 
Top Bottom